Improved design method for continuous-time quadrature bandpass ΣΔ ADCs

In continuous-time quadrature bandpass ΣΔ ADCs it is desirable to limit the number of cross-couplings. This can be achieved by implementing the loop as a cascade of complex integrators with only real coefficients. It is shown that this may result in a very poor approximation of the desired noise transfer function, because the effect of the DAC pulse is not taken into account correctly. A simple implementation that solves this problem is proposed.